I love Iris and Ian. They start with the same letter and have two syllables, yes, but with different vowel sounds. For me, if I had twins that shared a letter I wouldn't feel the need to continue that for the next kid.

I like Iris and Luke quite a bit, though the matching end sounds of Iris and Lucas bugs me a little. Then again, you could think of it as a connection between their names.

Iris is such a charming, surprising choice that hits right in the sweet spot for me—familiar but uncommon, delicate but spunky. Max feels common and expected by comparison, though it is cute.

I think Iris and Luca sound the best together. They both feel a tiny bit exotic, yet totally wearable. Special without being over-the-top. Lucas doesn't match as well because they both end in S. My 2nd choice would be Max, but I think Maximilian would be even better. Max feels a little overused. Ian also feels a little mundane. With Maximilian you could use Max or Ian as a nickname.